Can you edit your post to include the actual source in <readmore> tags? Many people won't bother to follow external links (arguably valid reasons being laziness, security, and/or just on principle), and also if the external link changes, this node becomes useless...

That aside, one quick code comment -- there's two spots where you're use $1, $2, and $3 from a s/// without first checking to see if the substitution works (and thus if $1/$2/$3 are what you expect)... (also, no div by zero check on $peak_percent assignment)